1. Field of the Invention
The present invention relates to temporary pacemakers, also known as wearable external pacemakers, and more particularly pertains to an external pacemaker that is VELCRO strapped to a patient's arm, chest or another portion of the body, using VELCRO or some other means.
2. Description of the Prior Art
There are several varieties of prior art pacemakers that are placed outside the body to be used temporarily while a patient is awaiting implantation of a permanent pacemaker or post-operative use. To use a prior art pacemaker, it is customary to connect a heart wire (hereinafter frequently designated as a lead) through the open chest and connect it to the heart or inserting a disposable lead transcutaneously, inserting it through a vein and into the heart. The external end of the lead or heart wire is, of course, attached to the pacemaker unit, so it follows that the unit must be positioned close to the patient. This is the first primary requirement of a temporary pacemaker.
External pacemakers of the prior art intended f or temporary use by new patients have been too bulky to be worn conveniently on the patient's body. In many instances, an extension cable is used between the lead or heart wire and the external pacemaker so that the pacemaker can be placed on an IV pole. As a result, the patient has been uncomfortably constrained by being connected by lead, heart wire, or cable to a comparatively immobile instrument. Added is the mental distress of knowing that even normal motion may dislodge the lead or heart wire with potentially hazardous results. Large control components--usually rotary switches and keyboards--are employed to make it easy for medical personnel to set pacing variables, but these also invite tampering by patient or visitors to the patient's room. Further, such components prevent adequate sterilization of the pacemaker before its use by a different patient. Added is the custom of using short-lived batteries, requiring routine instrument maintenance that sometimes is forgotten under stress, especially since personnel expected to perform it are unfamiliar with such procedures.
The second primary requirement is that a temporary pacemaker must be easily and readily adjustable. This must be done immediately after connection to the patient, and on some occasions, must be done on an emergency basis during the first crucial hours of a patient's experience with the pacemaker. Because of this requirement, the necessary controls are made relatively large and easy to manipulate. Usually, programming is accomplished by means of push buttons and rotary switches placed on one face of the enclosure. The same f ace of the box or enclosure must also support one or more readout displays as well. As a result of these combined factors, the temporary pacemaker is much larger than an implantable pacemaker.
These two requirements--proximity to the patient and ready programmability--lead to a series of design conflicts that have not been resolved in the prior art to date. The present invention, however, resolves all of them. The nature of these design conflicts can be appreciated from the following descriptions:
First, one would prefer to attach the temporary pacemaker (hereinafter frequently designated as a unit) to the patient's body, to avoid inadvertent tension on the lead or heart wire. Ideally, it would be attached to the patient's upper arm, chest, or leg using a snug but comfortable strap. Prior art units are much too large to make such a practice convenient or comfortable, however. As a result, the comparatively bulky unit is sometimes tied to the patient's bed, hung on an IV pole, or placed on a nearby table, with a connecting cable provided. With such arrangements, the patient is often unable to move in bed without the hazard of dislodging the lead, a fact that adds mental stress to physical discomfort. In other instances, especially for ambulatory patients, the unit is sometimes pinned to the patient's clothing. All of these arrangements require a longer lead than would a body-mounted unit, though, and both lead length and the relative immobility of the unit increase the possibility of accidentally stressing the lead or heart wire.
The second kind of conflict arises because having a readily adjustable unit situated very near the patient opens the possibility of tampering with the control settings by the patient or visitors. Experience shows that this is a genuine concern, even though it may seem at first to be an implausible one. Remedial changes, both in design and of an ad hoc kind, have proven unsatisfactory. A cover or interlock on the controls has been provided in some cases. But this places an extra burden on medical personnel, who must quickly release the lock, sometimes under stressful conditions. The same is true of interlock arrangements that must be negotiated before settings can be changed. When an unlocked cover is provided, medical personnel have been known to put tape over the cover to make it harder for the patient or visitors to change settings. But this is obviously an unsatisfactory solution, since time-consuming tape removal is a handicap, especially in emergencies, and also the presence of the tape interferes with vision in routine monitoring of the unit.
The third conflict arises because the unit is close to the patient and blood contact is inevitable in the use of the overall system. Therefore, a means of disinfecting the unit is called for by standards of sound medical practice before the same unit is used for a different patient, in spite of the fact that the lead used with the unit is disposable. Such standard practice in this case is augmented by widespread public anxiety concerning HIV infection and AIDS, where human blood is concerned. The units are much too expensive for casual disposal because they are relatively complex and are manufactured in small volumes. But these units are not sealed, so that disinfecting liquids cannot easily and effectively be used. The components cannot withstand temperatures even approaching autoclave temperatures. Furthermore, gas sterilization, although used, is unsatisfactory because literally days are required for "aeration", or permitting the toxic sterilizing gases to diffuse out of the many interstices inside the case.
A fourth shortcoming common to all prior art temporary pacemakers is unrelated to the conflicting requirements just cited. It is customary to employ comparatively short-lived batteries to power the unit, with the expectation that the batteries will be checked and usually changed for each new patient. But on occasion this routine step has been neglected with serious consequences. Longer-lived batteries are available, but are most compatible with smaller and more efficient systems.
The present invention resolves all of the conflicts just outlined. The essential innovation places the bulky control mechanisms in a unit that is separate and that never comes in contact with the patient. By means of infrared radiation, the temporary pacemaker communicates with a small, sealed unit worn by the patient. This resolves the tampering issue, the comfort and convenience issue, and the sterilization issue. In addition, the new, wearable unit of the invention is a natural recipient o.f a long-lived battery.